Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.82	6.383%	$222.149	$222.15	$222.15	$222.10
Purchase #2	$101.47	4.784%	$106.3243	$106.32	$106.30	$106.30
Purchase #3	$19.32	5.398%	$20.3629	$20.36	$20.35	$20.40
Purchase #4	$219.96	10.778%	$243.6673	$243.67	$243.65	$243.70
Purchase #5	$35.86	8.182%	$38.7941	$38.79	$38.80	$38.80
Purchase #6	$9.64	13.649%	$10.9558	$10.96	$10.95	$11.00
Purchase #7	$93.81	6.130%	$99.5606	$99.56	$99.55	$99.60
7 purchase totals =	$688.88		$741.8140	$741.81	$741.75	$741.90